Set up dependabot configuration to use PR prefix and labels

On-behalf-of: SAP <marvin.beckers@sap.com>
Signed-off-by: Marvin Beckers <marvin@kubermatic.com>

Author: embik

.github/dependabot.yaml

@@ -2,6 +2,15 @@ version: 2
 updates:
 # Maintain dependencies for GitHub Actions
 - package-ecosystem: "github-actions"
+  # Workflow files stored in the
+  # default location of `.github/workflows`
   directory: "/"
   schedule:
-    interval: "daily"
+    interval: "weekly"
+  groups:
+    all-github-actions:
+      patterns: [ "*" ]
+  commit-message:
+    prefix: ":seedling:"
+  labels:
+  - "ok-to-test"